1 /*
2 * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.swing.plaf;
27
28 import javax.swing.JComponent;
29 import javax.swing.SwingUtilities;
30 import javax.accessibility.Accessible;
31
32 import java.awt.Component;
33 import java.awt.Dimension;
34 import java.awt.Graphics;
35 import javax.swing.UIManager;
36 import sun.swing.SwingUtilities2;
37
38
39 /**
40 * The base class for all UI delegate objects in the Swing pluggable
41 * look and feel architecture. The UI delegate object for a Swing
42 * component is responsible for implementing the aspects of the
43 * component that depend on the look and feel.
44 * The <code>JComponent</code> class
45 * invokes methods from this class in order to delegate operations
46 * (painting, layout calculations, etc.) that may vary depending on the
47 * look and feel installed. <b>Client programs should not invoke methods
48 * on this class directly.</b>
49 *
50 * @see javax.swing.JComponent
51 * @see javax.swing.UIManager
52 *
53 */
54 public abstract class ComponentUI {
55
56 private TextUIDrawing textUIDrawing;
57
58 /**
59 * Sole constructor. (For invocation by subclass constructors,
60 * typically implicit.)
61 */
62 public ComponentUI() {
63 }
64
65 /**
66 * Configures the specified component appropriately for the look and feel.
67 * This method is invoked when the <code>ComponentUI</code> instance is being installed
68 * as the UI delegate on the specified component. This method should
69 * completely configure the component for the look and feel,
70 * including the following:
71 * <ol>
72 * <li>Install default property values for color, fonts, borders,
73 * icons, opacity, etc. on the component. Whenever possible,
74 * property values initialized by the client program should <i>not</i>
75 * be overridden.
76 * <li>Install a <code>LayoutManager</code> on the component if necessary.
77 * <li>Create/add any required sub-components to the component.
78 * <li>Create/install event listeners on the component.
79 * <li>Create/install a <code>PropertyChangeListener</code> on the component in order
80 * to detect and respond to component property changes appropriately.
81 * <li>Install keyboard UI (mnemonics, traversal, etc.) on the component.
82 * <li>Initialize any appropriate instance data.
83 * </ol>
84 * @param c the component where this UI delegate is being installed
85 *
86 * @see #uninstallUI
87 * @see javax.swing.JComponent#setUI
88 * @see javax.swing.JComponent#updateUI
89 */
90 public void installUI(JComponent c) {
91
92 if (textUIDrawing == null || textUIDrawing instanceof UIResource) {
93 textUIDrawing = (TextUIDrawing) UIManager.get("uiDrawing.text");
94 }
95
96 if (textUIDrawing == null) {
97 textUIDrawing = SwingUtilities2.DEFAULT_UI_TEXT_DRAWING;
98 }
99 }
100
101 /**
102 * Reverses configuration which was done on the specified component during
103 * <code>installUI</code>. This method is invoked when this
104 * <code>UIComponent</code> instance is being removed as the UI delegate
105 * for the specified component. This method should undo the
106 * configuration performed in <code>installUI</code>, being careful to
107 * leave the <code>JComponent</code> instance in a clean state (no
108 * extraneous listeners, look-and-feel-specific property objects, etc.).
109 * This should include the following:
110 * <ol>
111 * <li>Remove any UI-set borders from the component.
112 * <li>Remove any UI-set layout managers on the component.
113 * <li>Remove any UI-added sub-components from the component.
114 * <li>Remove any UI-added event/property listeners from the component.
115 * <li>Remove any UI-installed keyboard UI from the component.
116 * <li>Nullify any allocated instance data objects to allow for GC.
117 * </ol>
118 * @param c the component from which this UI delegate is being removed;
119 * this argument is often ignored,
120 * but might be used if the UI object is stateless
121 * and shared by multiple components
122 *
123 * @see #installUI
124 * @see javax.swing.JComponent#updateUI
125 */
126 public void uninstallUI(JComponent c) {
127 if (textUIDrawing instanceof UIResource) {
128 textUIDrawing = null;
129 }
130 }
131
132 /**
133 * Paints the specified component appropriately for the look and feel.
134 * This method is invoked from the <code>ComponentUI.update</code> method when
135 * the specified component is being painted. Subclasses should override
136 * this method and use the specified <code>Graphics</code> object to
137 * render the content of the component.
138 *
139 * @param g the <code>Graphics</code> context in which to paint
140 * @param c the component being painted;
141 * this argument is often ignored,
142 * but might be used if the UI object is stateless
143 * and shared by multiple components
144 *
145 * @see #update
146 */
147 public void paint(Graphics g, JComponent c) {
148 }
149
150 /**
151 * Notifies this UI delegate that it is time to paint the specified
152 * component. This method is invoked by <code>JComponent</code>
153 * when the specified component is being painted.
154 *
155 * <p>By default this method fills the specified component with
156 * its background color if its {@code opaque} property is {@code true},
157 * and then immediately calls {@code paint}. In general this method need
158 * not be overridden by subclasses; all look-and-feel rendering code should
159 * reside in the {@code paint} method.
160 *
161 * @param g the <code>Graphics</code> context in which to paint
162 * @param c the component being painted;
163 * this argument is often ignored,
164 * but might be used if the UI object is stateless
165 * and shared by multiple components
166 *
167 * @see #paint
168 * @see javax.swing.JComponent#paintComponent
169 */
170 public void update(Graphics g, JComponent c) {
171 if (c.isOpaque()) {
172 g.setColor(c.getBackground());
173 g.fillRect(0, 0, c.getWidth(),c.getHeight());
174 }
175 paint(g, c);
176 }
177
178 /**
179 * Returns the specified component's preferred size appropriate for
180 * the look and feel. If <code>null</code> is returned, the preferred
181 * size will be calculated by the component's layout manager instead
182 * (this is the preferred approach for any component with a specific
183 * layout manager installed). The default implementation of this
184 * method returns <code>null</code>.
185 *
186 * @param c the component whose preferred size is being queried;
187 * this argument is often ignored,
188 * but might be used if the UI object is stateless
189 * and shared by multiple components
190 * @return a {@code Dimension} object containing given component's preferred
191 * size appropriate for the look and feel
192 * @see javax.swing.JComponent#getPreferredSize
193 * @see java.awt.LayoutManager#preferredLayoutSize
194 */
195 public Dimension getPreferredSize(JComponent c) {
196 return null;
197 }
198
199 /**
200 * Returns the specified component's minimum size appropriate for
201 * the look and feel. If <code>null</code> is returned, the minimum
202 * size will be calculated by the component's layout manager instead
203 * (this is the preferred approach for any component with a specific
204 * layout manager installed). The default implementation of this
205 * method invokes <code>getPreferredSize</code> and returns that value.
206 *
207 * @param c the component whose minimum size is being queried;
208 * this argument is often ignored,
209 * but might be used if the UI object is stateless
210 * and shared by multiple components
211 *
212 * @return a <code>Dimension</code> object or <code>null</code>
213 *
214 * @see javax.swing.JComponent#getMinimumSize
215 * @see java.awt.LayoutManager#minimumLayoutSize
216 * @see #getPreferredSize
217 */
218 public Dimension getMinimumSize(JComponent c) {
219 return getPreferredSize(c);
220 }
221
222 /**
223 * Returns the specified component's maximum size appropriate for
224 * the look and feel. If <code>null</code> is returned, the maximum
225 * size will be calculated by the component's layout manager instead
226 * (this is the preferred approach for any component with a specific
227 * layout manager installed). The default implementation of this
228 * method invokes <code>getPreferredSize</code> and returns that value.
229 *
230 * @param c the component whose maximum size is being queried;
231 * this argument is often ignored,
232 * but might be used if the UI object is stateless
233 * and shared by multiple components
234 * @return a <code>Dimension</code> object or <code>null</code>
235 *
236 * @see javax.swing.JComponent#getMaximumSize
237 * @see java.awt.LayoutManager2#maximumLayoutSize
238 */
239 public Dimension getMaximumSize(JComponent c) {
240 return getPreferredSize(c);
241 }
242
243 /**
244 * Returns <code>true</code> if the specified <i>x,y</i> location is
245 * contained within the look and feel's defined shape of the specified
246 * component. <code>x</code> and <code>y</code> are defined to be relative
247 * to the coordinate system of the specified component. Although
248 * a component's <code>bounds</code> is constrained to a rectangle,
249 * this method provides the means for defining a non-rectangular
250 * shape within those bounds for the purpose of hit detection.
251 *
252 * @param c the component where the <i>x,y</i> location is being queried;
253 * this argument is often ignored,
254 * but might be used if the UI object is stateless
255 * and shared by multiple components
256 * @param x the <i>x</i> coordinate of the point
257 * @param y the <i>y</i> coordinate of the point
258 * @return {@code true} if the specified {@code x,y} location is contained
259 * within the look and feel's defined shape for the given component
260 * @see javax.swing.JComponent#contains
261 * @see java.awt.Component#contains
262 */
263 @SuppressWarnings("deprecation")
264 public boolean contains(JComponent c, int x, int y) {
265 return c.inside(x, y);
266 }
267
268 /**
269 * Returns an instance of the UI delegate for the specified component.
270 * Each subclass must provide its own static <code>createUI</code>
271 * method that returns an instance of that UI delegate subclass.
272 * If the UI delegate subclass is stateless, it may return an instance
273 * that is shared by multiple components. If the UI delegate is
274 * stateful, then it should return a new instance per component.
275 * The default implementation of this method throws an error, as it
276 * should never be invoked.
277 *
278 * @param c a {@code JComponent} for which to create a UI delegate
279 * @return a {@code ComponentUI} object for {@code c}
280 */
281 public static ComponentUI createUI(JComponent c) {
282 throw new Error("ComponentUI.createUI not implemented.");
283 }
284
285 /**
286 * Returns the baseline. The baseline is measured from the top of
287 * the component. This method is primarily meant for
288 * <code>LayoutManager</code>s to align components along their
289 * baseline. A return value less than 0 indicates this component
290 * does not have a reasonable baseline and that
291 * <code>LayoutManager</code>s should not align this component on
292 * its baseline.
293 * <p>
294 * This method returns -1. Subclasses that have a meaningful baseline
295 * should override appropriately.
296 *
297 * @param c <code>JComponent</code> baseline is being requested for
298 * @param width the width to get the baseline for
299 * @param height the height to get the baseline for
300 * @throws NullPointerException if <code>c</code> is <code>null</code>
301 * @throws IllegalArgumentException if width or height is < 0
302 * @return baseline or a value < 0 indicating there is no reasonable
303 * baseline
304 * @see javax.swing.JComponent#getBaseline(int,int)
305 * @since 1.6
306 */
307 public int getBaseline(JComponent c, int width, int height) {
308 if (c == null) {
309 throw new NullPointerException("Component must be non-null");
310 }
311 if (width < 0 || height < 0) {
312 throw new IllegalArgumentException(
313 "Width and height must be >= 0");
314 }
315 return -1;
316 }
317
318 /**
319 * Returns an enum indicating how the baseline of the component
320 * changes as the size changes. This method is primarily meant for
321 * layout managers and GUI builders.
322 * <p>
323 * This method returns <code>BaselineResizeBehavior.OTHER</code>.
324 * Subclasses that support a baseline should override appropriately.
325 *
326 * @param c <code>JComponent</code> to return baseline resize behavior for
327 * @return an enum indicating how the baseline changes as the component
328 * size changes
329 * @throws NullPointerException if <code>c</code> is <code>null</code>
330 * @see javax.swing.JComponent#getBaseline(int, int)
331 * @since 1.6
332 */
333 public Component.BaselineResizeBehavior getBaselineResizeBehavior(
334 JComponent c) {
335 if (c == null) {
336 throw new NullPointerException("Component must be non-null");
337 }
338 return Component.BaselineResizeBehavior.OTHER;
339 }
340
341 /**
342 * Returns the number of accessible children in the object. If all
343 * of the children of this object implement <code>Accessible</code>,
344 * this
345 * method should return the number of children of this object.
346 * UIs might wish to override this if they present areas on the
347 * screen that can be viewed as components, but actual components
348 * are not used for presenting those areas.
349 *
350 * Note: As of v1.3, it is recommended that developers call
351 * <code>Component.AccessibleAWTComponent.getAccessibleChildrenCount()</code> instead
352 * of this method.
353 *
354 * @param c {@code JComponent} for which to get count of accessible children
355 * @return the number of accessible children in the object
356 * @see #getAccessibleChild
357 */
358 public int getAccessibleChildrenCount(JComponent c) {
359 return SwingUtilities.getAccessibleChildrenCount(c);
360 }
361
362 /**
363 * Returns the <code>i</code>th <code>Accessible</code> child of the object.
364 * UIs might need to override this if they present areas on the
365 * screen that can be viewed as components, but actual components
366 * are not used for presenting those areas.
367 *
368 * <p>
369 *
370 * Note: As of v1.3, it is recommended that developers call
371 * <code>Component.AccessibleAWTComponent.getAccessibleChild()</code> instead of
372 * this method.
373 *
374 * @param c a {@code JComponent} for which to get a child object
375 * @param i zero-based index of child
376 * @return the <code>i</code>th <code>Accessible</code> child of the object
377 * @see #getAccessibleChildrenCount
378 */
379 public Accessible getAccessibleChild(JComponent c, int i) {
380 return SwingUtilities.getAccessibleChild(c, i);
381 }
382
383 /**
384 * Returns the {@code TextUIDrawing} instance responsible for text drawing
385 * and measuring.
386 *
387 * @return {@code TextUIDrawing} instance
388 *
389 * @since 9
390 */
391 public TextUIDrawing getTextUIDrawing() {
392 return textUIDrawing;
393 }
394 }